1. Field of the Invention
This invention relates to an electroconvergent cautery system employing forceps or probes which produce sharply localized heating for cutting, vaporizing tissue and coagulating blood vessels when brought into contact with the same.
2. Description of the prior art
Monopolar cautery systems have been in use for the last seventy to eighty years. Monopolar electrocautery systems are used for coagulating vessels and for cutting tissue. In the prior electrocautery systems, high frequency electric current is passed from the cautery probe through the tissue to the grounding pad. Heat is generated in the tissue at the site of contact of the probe tip to the tissue by the flow of current through the electrical resistance of the tissue in the preferred path between the probe tip contact site and the grounding pad. In such devices, the current is continuous sinusoidal or amplitude modulated. The heat generated by the cautery of the prior monopolar electrocautery systems is not uniform since the heating of the tissue is greater in the preferred path of current of lower resistance. For this reason, as the current flows from the point of contact of the probe to the surrounding tissue, heating also tends to spread beyond the contact point of the probe to the surrounding tissue thereby causing damage to the surrounding tissue. The problems associated with the prior monopolar electrocautery systems were overcome by the bipolar cautery system, which causes current to flow from one tip of the forceps to the other tip of the forceps without the spread of current to the surrounding tissues. Both the monopolar electrocautery and the bipolar cautery system can cut tissue and coagulate vessels but cannot vaporize tissue.
Radio frequency (RF) lesion generators work on the same principle as the monopolar cautery system except that a lower level of current is used and the current is of the continuoussinusoidal type resulting in more uniform tissue destruction. However, such a system is used exclusively for creating lesions.
In an effort to resolve the problems of the prior art, the inventors invented a radio frequency surgical tool which is disclosed in U.S. Pat. No. 5,019,076. The tool of U.S. Pat. No. 5,019,076 is capable of cutting and vaporizing tissue and coagulating vessels without the spread of heat to the surrounding tissue. In the device of said patent, a high frequency (13.56 or 27.0 MHz) current is passed through an amplifier, a matching network and a solenoid coil to generate an electromagnetic field. This in turn induces eddy currents in the tissue. Touching the tissue by a probe which is AC-coupled to a return circuit draws the eddy currents out of the tissue at the contact point of the probe producing intense heat which can cut and vaporize tissue as well as coagulate vessels. One disadvantage of the system of the said patent is the proximity of the coil in the operative field causing inconvenience to the surgeon. A further disadvantage of the device of said patent is that the coagulating ability of the device is not as efficient as desired.